Non-rigid and/or lighter-than-air airships are known such as gas balloons which have been provided in many shapes and sizes. Known designs are extremely bulky and have considerable drag if the motor is used for lateral propulsion. It would be advantageous to build a gas balloon or other type of airship which is more suited by its shape to be propelled with less drag. Such a shape would be streamlined by comparison with known balloon shapes and is preferably, therefore, of small dimensions in one coordinate direction such as a thin cross-section. It is, however, very difficult to construct from a soft fabric a balloon which will retain such a shape when inflated. More particularly, if the shape chosen is that of a disc or "flying saucer" shape, it is difficult to maintain a thin cross-section when the envelope is inflated.
It has also been previously known to provide lighter-than-air airships which can be propelled in a given direction and which are streamlined to promote propulsion in a given direction but which have fins or other guide surfaces to maintain stability. If a turn to the left or right is desired, it is usually necessary to bank one fin lower than the lower to initiate a turn. Consequently, sharp turns cannot be achieved.
It is known that a "flying saucer" shape is a desirable shape since it is streamline in all horizontal directions. However, up until now it has not been known how to maintain such a saucer-like shape in level flight.